The invention relates to an interconnection structure for connecting a conductor pattern associated with a substrate in an electrically conducting manner.
The relevant conductor pattern may form part of, for example, a semiconductor substrate (integrated circuit or a discrete semiconducotr element) or of a wiring pattern of, for example, glass, quartz, ceramic material, polyimide or other synthetic.
The invention also relates to a display device in which such an interconnection structure is used.
An interconnection structure of the type described in the opening paragraph, also referred to as a "bump", may be provided on a semiconductor substrate for mounting by means of the so-called flip-chip method (also referred to as face-down bonding). Such a structure is described in U.S. Pat. No. 4,749,120. An IC provided with such bumps is mounted on a glass substrate by means of said flip-chip method. In one of the mounting methods described in U.S. Pat. No. 4,749,120 an electrically conducting contact is first obtained between the bump and the conductor track by means of a pressure contact, whereafter the pressure of this contact is maintained by curing a resin layer provided between the substrate and the IC.
Such a mounting method is used, inter alia, in the manufacture of liquid crystal display devices (LCDs) in which ICs are secured by means of said flip-chip method on a substrate of glass or quartz which also forms part of the actual (liquid crystal) display device. Conductor tracks continuing as far as the actual display section are provided with drive voltages via the integrated circuits which contact these conductor tracks by means of said interconnection structures (or bumps).
However, a number of problems may occur. A first problem occurs, for example, when contacting integrated circuits with many bumps, where different types of conductor tracks are present on the substrate, for example, indium tin oxide tracks for driving pixels in addition to, for example, aluminium tracks. A possible difference in thickness between the different types of conductor tracks may give rise to poor or open contacts, notably in the case of pressure contacts.
Moreover, if no special measures are taken, the actual contact of the interconnection structure with, for example, a thin connection conductor may remain limited to a very small area (for example, a projecting point of the bump), which leads to a high contact resistance. This notably occurs when a low pressure is used for contacting, for example, for test purposes. Such high contact resistances may subsist also after mounting.